Avocado in Final Space. His whole death scene was a gut punch. After finally getting his son back, beating the baddie. The baddie slips an explosive onto his sons back as the heroes escape but no one sees it. Everyone is celebrating that they got out and a lot of the audio in that scene is muted.

Nobody notices the explosive on the son's back, but avocado does so he tells everyone to take care of his son as he sacrifices himself by getting the explosive away from everyone. The episode credits roll with a shadowed image of his son standing in front of the hole in the hull of the ship from the explosion. And from what I heard, the channel it was on had a funeral for him that was outside of the show's universe.

Also, the main characters father. Later they have to go back in time to stop the main baddie and he meets his dad. Who had died when the main character was really young. They spend a solid half of the episode boning, they turn out to be a lot alike. And in the end his dad still has to die and there was no way tot avoid it.